Process for separating and recovering 3-hydroxypropionic acid and acrylic acid

ABSTRACT

Disclosed is a process for separating and recovering 3-hydroxypropionic acid from an aqueous solution comprising 3-hydroxypropionic acid and acrylic acid, comprising counter current extracting the aqueous solution with ethyl acetate extractant. Further disclosed is a process for separating and recovering 3-hydroxypropionic acid and acrylic acid from an aqueous solution comprising 3-hydroxypropionic acid and acrylic acid.

CROSS REFERENCE TO RELATED APPLICATIONS

This is the U.S. National Stage of International Application No.PCT/US2004/020580, filed Jun. 25, 2004, which in turn claims the benefitof U.S. Provisional Application No. 60/482,815 filed Jun. 26, 2003, theentire contents of which are incorporated herein by reference.

FIELD

This invention relates to a process for separating and recovering3-hydroxypropionic acid from an aqueous solution comprising3-hydroxypropionic acid, acrylic acid and/or other acid impurities. Theaqueous solution may be obtained from anyone of multiple preparationroutes of 3-hydroxypropionic acid, including hydration of acrylic acid.

Furthermore, the invention relates to combining both the process forseparating and recovering 3-hydroxypropionic acid and a process forseparating and recovering acrylic acid. This allows for the recycling ofacrylic acid, and organic extractant, providing economic advantages. Theprocesses for separating and recovering acrylic acid from solutionscomprising acrylic acid and an organic extractant are as follows. In afirst process, a solution comprising acrylic acid and an organicextractant is subjected to back extraction with water to recover theacrylic acid from the extractant. In another process, a solutioncomprising acrylic acid and an organic extractant having a boiling pointlower than 100° C. is distilled in the presence of water to distill theextractant, resulting in an aqueous acrylic acid solution.

BACKGROUND

Various methods for separating and recovering 3-hydroxypropionic acidfrom an aqueous solution comprising 3-hydroxypropionic acid and acrylicacid are known. Included within such methods is distilling acrylic acidfrom the aqueous solution. Further, it is known that acrylic acid in theaqueous solution is extracted with ethyl acetate as an extractant in across current manner. This is described in a publication by Shem,Changzhou, You, Sihui; Huaxueshijie, 1997, 19 (2), pg 77-79.

SUMMARY

The present invention provides batch and continuous processes forseparating and recovering 3-hydroxypropionic acid from an aqueoussolution comprising 3-hydroxypropionic acid, acrylic acid and/or otheracid impurities by a counter current mode solvent extraction with ethylacetate as the organic extractant, that allows for separation andrecovery of 3-hydroxypropionic acid. In addition, the present inventionprovides a process for separating and recovering 3-hydroxypropionic acidin high efficiency, at a high yield, and at high purity.

Additionally, the present invention provides a process for separatingand recovering 3-hydroxypropionic acid from an aqueous solutioncomprising 3-hydroxypropionic acid, acrylic acid, and/or other acidimpurities, that also includes the separation and recovery of acrylicacid from solutions comprising acrylic acid and an organic extractant,and regenerating extractant for reuse.

In one embodiment the present invention provides a process forextracting acrylic acid and/or other acid impurities from an aqueoussolution also containing 3-hydroxypropionic acid with ethyl acetateextractant using a counter current manner. Acrylic acid may be recoveredfrom the extractant thereby enabling the extractant and acrylic acid tobe recycled for reuse. The aqueous solution remaining after acrylic acidextraction by the ethyl acetate extractant comprises 3-hydroxypropionicacid. The extraction is conducted in a counter current manner utilizingany equipment such that the separation and recovery of3-hydroxypropionic acid from acrylic acid can be achieved.

Another embodiment of the present invention comprises combining theprocess for separating and recovering 3-hydroxypropionic acid from asolution comprising 3-hydroxypropionic acid and acrylic acid, utilizinga counter current mode extraction with ethyl acetate, with a process forseparating and recovering acrylic acid from a solution comprisingacrylic acid and ethyl acetate extractant. This combined process allowsfor recovering and recycling acrylic acid and/or extractant, providingeconomic advantage. These are two processes for separating andrecovering acrylic acid from a solution comprising acrylic acid andethyl acetate extractant. A first process comprises subjecting asolution comprising acrylic acid and extractant to back extraction withwater, using any conventional technique, to separate and recover theacrylic acid from the extractant. A second process for separating andrecovering acrylic acid from a solution comprising acrylic acid andethyl acetate extractant comprises distilling the solution, in thepresence of water, to distill the extractant, thereby resulting in anaqueous acrylic acid solution.

The 3-hydroxypropionic acid recovered by the present process is a knowncompound having many applications, and the product herein is useful insuch applications. In particular, 3-hydroxypropionic acid is known to beuseful in the preparation of polymeric materials, and as being usefulintermediates in the preparation of various organic materials.

DETAILED DESCRIPTION

In accordance with the present invention, it has been found that theabove and still further objects are achieved by counter current modeextracting acrylic acid and/or other acid impurities from an aqueoussolution also containing 3-hydroxypropionic acid with an ethyl acetateas the organic extractant. Acrylic acid may be recovered from theorganic extractant thereby enabling the organic extractant and acrylicacid to be recycled for reuse. The aqueous solution remaining afteracrylic acid extraction by the organic extractant comprises3-hydroxypropionic acid.

The extraction is conducted in a counter current manner, utilizing anyequipment such that the separation and recovery of 3-hydroxypropionicacid from acrylic acid can be achieved.

Another embodiment of the present invention comprises combining theprocess for separating and recovering 3-hydroxypropionic acid from asolution comprising 3-hydroxypropionic acid and acrylic acid, utilizinga counter current mode extraction with ethyl acetate, with a process forseparating and recovering acrylic acid from a solution comprisingacrylic acid and ethyl acetate extractant. This combined process allowsfor recovering and recycling acrylic acid and/or extractant, providingeconomic advantage. There are two exemplary processes for separating andrecovering acrylic acid from a solution comprising acrylic acid andethyl acetate extractant. A first process comprises subjecting asolution comprising acrylic acid and extractant to back extraction withwater, using any conventional technique, to separate and recover theacrylic acid from the extractant. A second process for separating andrecovering acrylic acid from a solution comprising acrylic acid andethyl acetate extractant comprises distilling the solution, in thepresence of water, to distill the extractant, thereby resulting in anaqueous acrylic acid solution.

In the process for separating and recovering the 3-hydroxypropionic acidby counter current mode extraction from the solution comprising3-hydroxypropionic acid and acrylic acid, the ethyl acetate for acrylicacid extraction in the organic phase is present in an amount of about 1to about 100 weight percent. The remainder of the component in theorganic phase is a saturated or unsaturated hydrocarbon solvent.

The counter current extraction of acrylic acid and/or other acidimpurities, from the solution comprising 3-hydroxypropionic acid, iscarried out at a temperature ranging from about 0° C. to about 70° C.,preferably from about 20° C. to about 40° C., and more preferably fromabout 20° C. to about 25° C. The volume ratio of the organic phase tothe aqueous phase in the extraction stage ranges from about 20:1 toabout 1:20, preferably from about 10:1 to about 1:10, and morepreferably from about 5:1 to about 1:5. The extraction is carried out incounter current manner and utilizes any extraction apparatus. Theextraction is carried out for any period of time such that theextraction is achieved. For example, the extraction may be carried outin a multistage extraction column, in a counter current manner.

Remaining after the aqueous phase comprising the 3-hydroxypropionic acidis separated, is an organic phase that comprises acrylic acid and/orother acid impurities, and ethyl acetate extractant In one embodimentfor separating and recovering the acrylic acid from the solutioncomprising acrylic acid and extractant, the solution is back extractedwith water. Accordingly, the acrylic acid is recovered from the organicphase, and the ethyl acetate extractant is regenerated. The regeneratedextractant may be recycled for use in the separation and recovery of the3-hydroxypropionic acid. The back extraction of the acrylic acid ethylacetate extractant solution is carried out at a temperature ranging fromabout 0° C. to about 180° C., preferably from about 50° C. to about 140°C. The volume ratio of the organic phase to the aqueous phase rangesfrom about 20:1 to about 1:20, preferably from about 10:1 to about 1:10,and more preferably from about 5:1 to about 1:5. The back extractionwith water is carried out in any manner and with any extractionequipment in any period of time such that the back extraction isachieved. For example, the back extraction may be carried out in amultistage extraction column in counter current, co-current or crosscurrent manner.

In another embodiment for separating and recovering acrylic acid from asolution comprising acrylic acid, ethyl acetate extractant and/or otheracid impurities, the organic phase that contains mainly acrylic acid andother acid impurities is subjected to distillation of ethyl acetateextractant, in the presence of water. The distilled extractant may berecycled back to the extraction for reuse to extract acrylic acid. Thedistillation of extractant may be carried out, in the presence of water,in accordance with any manner, under any conditions, such that thedistillation is achieved. For example, the distillation of extractantmay be carried out at any pressure, and at any temperature. The volumeratio of the organic phase to the aqueous phase in the extraction stageranges from about 20:1 to about 1:20, preferably from about 10:1 toabout 1:10, and more preferably from about 5:1 to about 1:5.

The counter current extraction is carried out in accordance with anymanner and with any extraction equipment in any period of time such thatthe extraction is achieved. For example, the extraction may be carriedout in a multistage extraction column in counter current manner. Thedistillation of extractant may be carried out in accordance with anymanner at any conditions such that the distillation is achieved.

The process for separating and recovering 3-hydroxypropionic acid hereinby counter current solvent extraction using ethyl acetate, from asolution comprising 3-hydroxypropionic acid, acrylic acid and/or otheracid impurities, may be combined with any of the processes herein forseparating and recovering acrylic acid from ethyl acetate extractantsolutions containing the acrylic acid. The processes may be combined inany manner to provide an economic advantage by allowing recovery andreuse of acrylic acid and extractant.

It has been found that the present process of solvent extraction withethyl acetate in a counter current manner results in a usage of ethylacetate that is about five (5) times less than the amount of ethylacetate utilized when the extraction is carried out in cross currentmanner.

The invention will be more readily understood by reference to thefollowing examples. There are, of course, many other forms of thisinvention which will become obvious to one skilled in the art, once theinvention has been fully disclosed, and it will accordingly berecognized that these examples are given for the purpose of illustrationonly, and are not to be construed as limiting the scope of thisinvention in any way.

EXAMPLES

In the following examples, products are analyzed by high pressure liquidchromatography (HPLC), described as follows:

High Pressure Liquid Chromatography (HPLC)

HPLC—the products produced by the process are analyzed using a Waters1525 Binary HPLC pump, equipped with a Waters 717 plus Autosampler, andWaters 2410 Refractive Index and Waters 2487 Dual Lambda Absorbancedetectors, having a Bio-Rad HP87-H column, 0.004 N sulfuric acid as themobile phase, a flow rate of 0.6 ml/min, and a column temperature of 60°C.

Example 1

In this example, there were utilized five (5) aqueous stock solutions.The aqueous stock solutions comprise 30% 3-hydroxypropionic acid aqueoussolution and 99% acrylic acid. In each of the five aqueous stocksolutions, the concentration of 3-hydroxypropionic acid is approximatelytwo times higher than the concentration of the acrylic acid. The aqueousstock solutions are shown in the following Table 1.

TABLE 1 Concentration of acrylic acid and 3-hydroxypropionic acid instock solutions. Conc. of 3- Conc. of total Aqueous Conc. of acrylichydroxypropionic acids in Stock acid in stock acid in stock stocksolution, Solution No. solution, wt. % solution, wt. % wt. % 1 0.67 1.342.01 2 3.33 6.67 10.00 3 6.67 13.34 20.01 4 9.99 19.98 29.97 5 12.5125.05 37.56The extraction procedure utilized in Examples 1-5 for separating andrecovering 3-hydroxypropionic acid and acrylic acid from aqueoussolutions comprising 3-hydroxypropionic acid and acrylic acid is carriedout as follows:

1. To a 15 ml centrifuge tube 5 ml of each acid stock solution and ethylacetate extractant were added. Masses of the empty centrifuge tube, theaqueous solution and extractant were recorded.

2. The tube was placed on a platform shaker and the contents in the tubewere mixed at 230 rpm for 30 minutes at 22° C. (rpm designatesrevolutions per minute).

3. At the end of mixing, the tube was centrifuged at 4500 rpm for 5minutes.

4. The volumes of the aqueous and ethyl acetate extractant phases in thetubes were recorded.

5. The aqueous phase was separated from the ethyl acetate extractantphase and the masses of both phases were recorded.

6. The acrylic acid and the 3-hydroxypropionic acid in the aqueoussolution were analyzed by HPLC.

7. The concentrations of acrylic acid and 3-hydroxypropionic acid in theethyl acetate extractant were calculated by subtracting theconcentrations of acrylic acid and 3-hydroxypropionic acid in theaqueous phase from the initial concentration in the stock solution.

The processing conditions and experimental results for the extraction ofacrylic acid (AA) and 3-hydroxypropionic acid (3HP) by ethyl acetate arereported in the following Table 2.

TABLE 2 Extraction of Acrylic Acid (AA) and 3-Hydroxypropionic Acid(3HP) from aqueous stock solutions Containing AA and 3HP by EthylAcetate Acid in Ethyl Aqueous Acetate Partition Stock Acid in AqueousExtractant Coefficient, Separation Example Solution, Phase, wt % Phase,wt % D¹ Factor, S² No. No. AA 3HP AA 3HP AA 3HP AA/3HP 1 1 0.20 1.130.59 0.20 2.96 0.18 16.55 2 2 0.97 5.77 2.87 1.21 2.97 0.21 14.18 3 32.02 11.38 5.36 3.09 2.66 0.27 9.79 4 4 3.18 17.08 7.53 5.17 2.36 0.307.81 5 5 4.22 21.16 8.07 8.68 1.91 0.41 4.66 ¹Partition coefficient, D,was calculated by dividing the acid concentration in the ethyl acetateextractant phase by the acid concentration in the aqueous phase, for AAand 3HP. ²Separation factor, S, was calculated by dividing the partitioncoefficient of the acrylic acid by the partition coefficient of 3HP.Comparison of Countercurrent Extraction with Crosscurrent Extraction

A comparison between a countercurrent extraction and a crosscurrentextraction with ethyl acetate as extractant for the separation andrecovery of 3-hydroxpropionic acid was done through calculation by usingthe known method published in the literature (L. Alders, “Liquid-LiquidExtraction; Theory and Laboratory Practice”, second, revised edition,Elsevier Publishing, 1959, page 103-106). In the calculation thefollowing assumptions were made:

-   -   1. Partition coefficients, D, for both acrylic acid and 3HP were        assumed to be constants and an average number of partition        coefficients listed in Table 2 was used. For acrylic acid,        D_(AA)=2.572 and for 3HP, D_(3HP)=0.274.    -   2. Phase ratio, R, equals extractant flow rate divided by        aqueous flow rate.    -   3. Solubilities of aqueous phase into extractant phase and        extractant phase into aqueous phase that may change the flow        rate of each phase were not considered in the calculation of        phase ratio, R.    -   4. An initial aqueous solution contains 20 wt % of 3HP and 10 wt        % acrylic acid.

Extraction factor for acrylic acid at each stage was calculated by usingE_(AA)=D_(AA)×R and extraction factor for 3HP at each stage wascalculated by using a formula of E_(3HP)=D_(3HP)×R.

For crosscurrent extraction, the fraction for acrylic acid not extractedat each stage is calculated by a formula of F_(AA)=1/(E_(AA)+1) in whichE_(AA) is extraction factor for acrylic acid at each stage.

For crosscurrent extraction, the fraction for 3HP not extracted at eachstage is calculated by a formula of F_(3HP)=1/(E_(3HP)+1) in whichE_(3HP) is extraction factor for 3HP at each stage.

For countercurrent extraction, the fraction for acrylic acid notextracted at each stage is calculated by a formula ofF_(AA)=(E_(AA)−1)/(E_(AA) ^(a+1)−1) in which E_(AA) is extraction factorfor acrylic acid at each stage and E_(AA) ^(n+1) is n+1 power ofextraction factor for acrylic acid at each stage, where n=number ofstage (for example, at first stage n=1 and at second stage n=2, and thelike).

For countercurrent extraction, the fraction for 3HP not extracted ateach stage is calculated by a formula of F_(3HP)=(E_(3HP)−I)/(E_(3HP)^(n+1)−I) in which E_(3HP) is extraction factor for 3HP at each stageand E_(3HP) ^(n+1) is n+1 power of extraction factor for 3HP at eachstage, where n=number of stage (for example, at first stage n=1 and atsecond stage n=2, and the like).

The results of the calculation by applying the above assumptions andformulas are presented in the following Table 3-6.

TABLE 3 Crosscurrent Extraction of 3HP and Acrylic Acid with EthylAcetate Fraction not Fraction not 3HP purity, 3HP yield, Stage extractedfor 3HP extracted for AA % % 0 66.67 100.00 1 0.773 0.266 85.31 77.33 20.773 0.266 94.40 59.80 3 0.773 0.266 98.00 46.24 4 0.773 0.266 99.3035.76 5 0.773 0.266 99.76 27.65 6 0.773 0.266 99.92 21.38

TABLE 4 Countercurrent Extraction of 3HP and Acrylic Acid with EthylAcetate Fraction not Fraction not 3HP purity, 3HP yield, Stage extractedfor 3HP extracted for AA % % 0 66.67 100.00 1 0.773 0.266 85.31 77.33 20.725 0.088 94.27 72.51 3 0.712 0.031 97.87 71.21 4 0.708 0.011 99.2270.84 5 0.707 0.004 99.72 70.73 6 0.707 0.001 99.90 70.70

Table 3 is an example of six-stage crosscurrent extraction with anaqueous flow rate of 1000 kg/hr and an extractant flow rate of 1070kg/hr. The aqueous solution contains 20% 3-hydroxypropionic acid and 10%acrylic acid. After six stages of crosscurrent extraction the 3HPproduct reaches a purity of 99.92% with a yield of 21.38%. A usage ofethyl acetate in the six stages of crosscurrent extraction is 6420kg/hr.

While in an identical run as in crosscurrent extraction, a six-stagecountercurrent extraction as showed in Table 4 produces the 3BP producthaving the same purity of 99.90% with a yield of 70.70% (3.3 timeshigher than one in crosscurrent extraction). A usage of ethyl acetate inthe six stages of countercurrent extraction is 1070 kg/hr (6 times lessthan one in crosscurrent extraction).

Table 5 and Table 6 show a comparison of crosscurrent extraction withcountercurrent extraction with about the same yield of 3HP product andthe same amount of ethyl acetate extractant, but the product purity onlyreaches 88.37% after six stages of crosscurrent extraction. The 3HPproduct after six stages of countercurrent extraction reaches a purityof 99.01%.

TABLE 5 Crosscurrent Extraction of 3HP and Acrylic Acid with EthylAcetate Fraction not Fraction not 3HP purity, 3HP yield, Stage extractedfor 3HP extracted for AA % % 0 0.970 0.777 66.67 100.00 1 0.970 0.77771.42 97.03 2 0.970 0.777 75.73 94.15 3 0.970 0.777 79.59 91.36 4 0.9700.777 82.97 88.64 5 0.970 0.777 85.88 86.01 6 0.970 0.777 88.37 83.46

TABLE 6 Countercurrent Extraction of 3HP and Acrylic Acid with EthylAcetate Fraction not Fraction not 3HP purity, 3HP yield, Stage extractedfor 3HP extracted for AA % % 0 66.67 100.00 1 0.845 0.367 82.16 84.49 20.822 0.175 90.35 82.15 3 0.817 0.092 94.65 81.73 4 0.817 0.051 96.9881.66 5 0.816 0.029 98.28 81.65 6 0.816 0.016 99.01 81.64

Example 2

This example shows the distillation of ethyl acetate loaded with acrylicacid. In a 100 ml round bottom flask is placed 18.5 grams ethyl acetate,3 grams of acrylic acid and 9 grams of distilled water. Reduced pressure(about 100 mmHg) is applied to the flask for the distillation of ethylacetate at room temperature (about 20-24° C.). The distillation iscompleted in about 5 minutes. Both the ethyl acetate distillatecollected and the remaining aqueous solution in the flask are weighedand the concentrations of acrylic acid in both ethyl acetate distillateand the aqueous solution are determined by means of titration. Theamount of acrylic acid remaining in the flask as the aqueous solution is91%. About 7% acrylic acid is co-distilled with ethyl acetate with asmall portion of water.

Example 3

An aqueous solution containing 10 wt % acrylic acid and 20 wt %3-hydroxypropionic acid is fed into a six-stage countercurrentextraction column at a flow rate of 1000 kg/hr. Ethyl acetate extractantis fed into the six-stage countercurrent extraction column at a flowrate of 1070 kg/hr. After six stage countercurrent extraction, theaqueous stream is expected to contain 3-hydroxypropionic acid productwith 99.9% purity. The yield of 3-hydroxypropionic acid product isexpected to be 70.70%. After the six stage countercurrent extraction theethyl acetate extractant stream is expected to contain about 9.3 wt %acrylic acid and 5.5 wt % 3-hydroxypropionic acid.

The above acrylic acid and 3-hydroxypropionic acid loaded ethyl acetatestream is mixed with distilled water at a ratio of 10 to 3 (extractantto water), and introduced into a container. The ethyl acetate is removedby distillation at a reduced pressure of about 100 mm Hg, and roomtemperature. The aqueous solution remaining in the flask is expected tocontain about 21 wt % acrylic acid and about 12 wt % 3-hydroxypropionicacid. The aqueous solution of acrylic acid and 3-hydroxypropionic acid,and the distilled ethyl acetate are recycled.

The invention has been described above in detail with particularreference to specific embodiments thereof, but it will be understoodthat variations and modifications other than as specifically describedherein can be effected within the spirit and scope of the invention.

1. A process comprising separating and recovering 3-hydroxypropionic acid from an aqueous solution comprising 3-hydroxypropionic acid and acrylic acid, via counter currently extracting the aqueous solution with an organic phase comprising ethyl acetate extractant.
 2. The process according to claim 1, wherein the ethyl acetate extractant is present in the organic phase in an amount ranging from about 1 to about 100 weight percent.
 3. The process according to claim 1, wherein, without further purification, the recovered 3-hydroxypropionic acid is at least about 80% pure when separated from the aqueous solution.
 4. The process according to claim 1, wherein the volume ratio of organic phase to aqueous solution ranges from about 20:1 to about 1:20.
 5. A process comprising separating and recovering 3-hydroxypropionic acid and acrylic acid from an aqueous solution comprising 3-hydroxypropionic acid and acrylic acid, including: (a) counter currently extracting the aqueous solution with an organic phase comprising ethyl acetate to extract the acrylic acid from the aqueous phase and into the organic phase and to separate the acrylic acid from the 3-hydroxypropionic acid; and (b) contacting the organic phase formed in step (a) with water to extract the acrylic acid from the organic phase and into the water.
 6. The process according to claim 5, wherein the ethyl acetate is present in the organic phase in an amount ranging from about 1 to about 100 weight percent.
 7. A process comprising separating and recovering 3-hydroxypropionic acid and acrylic acid from an aqueous solution comprising 3-hydroxypropionic acid and acrylic acid, including: (a) counter currently extracting the aqueous solution with an organic phase comprising ethyl acetate, to extract the acrylic acid from the aqueous solution into the organic phase and to separate the acrylic acid from the 3-hydroxypropionic acid; and (b) heating the organic phase formed in step (a), in the presence of water, to distill off the ethyl acetate, thereby forming an aqueous acrylic acid solution. 